DQDB 城域网 PPAU 软件设计

PPAU Software Design for DQDB Metropolitan Area Networks

城域网也称都市网或城市网，是近年来计算机网络领域出现的一个新的分支，是在已经得到广泛应用的广域网（ＷＡＮ）和局域网（ＬＡＮ）基础上发展起来的一种新型的计算机网络。目前国内正在开展对ＤＱＤＢ的研究和相关的产品开发。分组处理访问单元ＰＰＡＵ属于ＤＱＤＢ协议ＭＡＣ汇聚功能，主要处理ＤＱＤＢ网上非连续性的异步数据。本文设计实现了ＤＱＤＢ网分组处理访问单元ＰＰＡＵ软件。文中着重讨论了ＰＰＡＵ的功能与运行环境，ＰＰＡＵ与总线驱动卡的接口，ＰＰＡＵ对上层服务数据的处理，以及ＰＰＡＵ软件实现中遇到的其他问题及其解决方法。

Metropolitan area network(MAN) is a new branch of the computer networks appearing in recent years. It is developed on the basis of the widely used wide area network(WAN)and local area network(LAN). At present, researches concerning the DQDB protocal and its related products have been widely carried out in our country. Packet processing access unit(PPAU)serves as the MAC aggregation function of the DQDB protocal. The main function of PPAU is to process the inconsecutive, asynchronous data on the DQDB network. The article designs and implements the PPAU software in a DQDB network, and discusses in detail the functions and operation environment of PPAU, the interface between the PPAU and the bus driver cards, the PPAU′s processing of the upper layer′s service data, and other implementation problems with their solutions.